Frequency sub-band coding of digital signals

ABSTRACT

A transmitter, using frequency sub-band coding, can output a plurality of narrowcast and/or broadcast signals to a plurality of sub-groups or nodes along a single optical link. The transmitter can output the plurality of signals as multiple slices of spectrum, wherein each slice of spectrum is designated for a particular sub-group or node. The transmitter can further instruct each receiver or node as to which slice of spectrum to use and at which frequency to output the associated signal information to its intended subscribers. Thus, a single transmitter can feed narrowcast information to multiple nodes or receivers along a single optical link. In embodiments, channels can be monitored and manipulated on a channel-by-channel basis, and channels delivered using different network solutions can be combined.

CROSS REFERENCE TO RELATED APPLICATION

This application is a non-provisional application claiming the benefitof U.S. Provisional Application Ser. No. 61/866,659, entitled “BroadbandDigital Forward,” which was filed on Aug. 16, 2013, and is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

This disclosure relates to sub-band coding of signals.

BACKGROUND

U.S. patent application Ser. No. 13/175,681 (“the '681 patentapplication”), filed Jul. 1, 2011, entitled, “Overlay System WithDigital Optical Transmitter For Digitized Narrowcast Signals,” which isincorporated herein by reference in its entirety, discloses variousimplementations of improved cable-based overlay systems used to deliverhigh-definition digital entertainment and telecommunications such asvideo, voice, and high-speed Internet services from a headend tosubscribers.

The implementations of the improved overlay system disclosed in the '681patent application operate to combine a digitally transported digitizednarrowcast transmission with a broadcast transmission that isamplitude-modulated and transported on an analog optical link on aseparate, dedicated fiber. Separate transport mechanisms for broadcastand narrowcast transmissions creates a need for more network resourcesand also results in a less than optimal use of a network system'sbandwidth capabilities. Therefore, a need exists for improving methodsand systems for delivering narrowcast and broadcast transmissions to asubscriber.

In general, a large amount of information is broadcast to an entiregroup of subscribers, and a relatively small fraction of information isnarrowcast to small sub-groups of subscribers, wherein each sub-group(e.g., represented by a node or node port) receives narrowcastinformation that is unique to the sub-group. Typically, the delivery ofa unique narrowcast transmission to a sub-group requires a narrowcasttransmitter and an optical wavelength that is dedicated to thesub-group, and dedicated to said sub-group alone. For example, currentoptical architectures require at least one narrowcast transmitter andone optical wavelength per sub-group (e.g., node or node port).Therefore, a need exists for creating greater efficiency in the use ofnarrowcast transmitters and for allowing a narrowcast transmitter and anoptical wavelength to serve more than one node or node port.

Typically, a CMTS transforms a signal into the time domain (e.g., usingan inverse fast Fourier transform (IFFT)) before outputting the signalto a transmitter. The transformed signal is then transported to atransmitter and then output to a receiver. Transporting,re-transforming, and compressing data received from the CMTS requires alarge amount of network and network component resources. Therefore, aneed exists for improving the transport of data from a CMTS to adownstream component.

Generally, optical networks do not provide independent control oradaptation to individual channel amplitude and performancecharacteristics. This lack of control and resulting insufficient marginsin forward and return traffic along the optical networks, can lead tothe need for reserving large amounts of headroom to account forworst-case scenarios. Remote PHY (physical layer) architecturestypically attempt to resolve the headroom issue by placing modulationand demodulation remotely at nodes. However, placing modulation anddemodulation at nodes comes at the expense of a loss in transparency andof incompatibility with existing RF system components. Therefore, a needexists for improving forward and reverse transmissions through anoptical fiber system.

Typically, return link transmitters are designed for a specificnoise-to-power ratio (NPR) (e.g., 40 dB NPR) in a significant dynamicwindow (e.g., 15 dB dynamic window) to account for set up issues and toprovide immunity from ingress clipping events. In embodiments, datainputs can be compressed such that NPR is maintained within a linkcapacity and within an associated dynamic window. For example, broadbandcompanding is a lossy compression method that can be applied to limitbitrates in return transmitters. In embodiments, when ingress is presentor when one or more channels are relatively strong compared to others,the noise of the companding process impacts the other channels (e.g.,the weaker channels) and achievable modulation error ratio (MER) for theother channels is reduced. In practice, the 40 dB NPR is generallyunavailable for weaker channels in the presence of strong channels whenall are residing within the proper radio frequency (RF) level set-upwindow. Therefore, a need exists for improved data compression tosupport combining and transporting broadband compressed forward (BCF)and remote physical layer (R-PHY) channels.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an example network environmentoperable to facilitate converting an analog broadcast signal into adigital broadcast signal.

FIG. 2 is a flowchart illustrating an example process operable tofacilitate converting an analog broadcast signal into a digitalbroadcast signal and combining the digital broadcast signal with one ormore digital narrowcast signals.

FIG. 3 is a block diagram illustrating an example network environmentoperable to facilitate transporting a plurality of narrowcasttransmissions using a single transmitter.

FIG. 4 is a flowchart illustrating an example process operable tofacilitate transporting a plurality of narrowcast transmissions using asingle transmitter.

FIG. 5 is a block diagram illustrating an example network environmentoperable to facilitate the downstream transporting and processing ofIFFT input data.

FIG. 6 is a block diagram illustrating an example network environmentoperable to facilitate the downstream transporting and processing ofIFFT input data.

FIG. 7 is a flowchart illustrating an example process operable tofacilitate the downstream transporting and processing of IFFT inputdata.

FIG. 8 is a block diagram illustrating an example transmitter operableto facilitate sub-band coding, monitoring, and compression.

FIG. 9 is a flowchart illustrating an example process operable tofacilitate transporting compressed digital forward signals along one ormore optical links.

FIG. 10 is a block diagram of a hardware configuration operable tofacilitate the transport of broadband digital forward data.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

It is desirable to improve upon methods and systems for deliveringnarrowcast and broadcast transmissions to a subscriber. Methods andsystems are described herein for digitizing a broadcast transmission andtransporting the digitized broadcast transmission along with one or moredigitized narrowcast transmissions to a subscriber. In embodiments, adigitized broadcast transmission and one or more digitized narrowcasttransmissions can be separately demodulated and the transmissions can becombined at one or more receiving nodes. In embodiments, a digitizedbroadcast transmission can be combined with one or more digitizednarrowcast transmissions.

Methods and systems described herein provide for network resource andhardware savings relative to analog broadcast/narrowcast overlay systemswherein the broadcast signal may be operated at high power and thusrequiring a separate fiber. Digital links can operate at lower powerlevels than analog systems, and a greater number of wavelengths can becombined on a single fiber while providing allowance for fibernonlinearity or optical component performance. Further, digital channelscan be delivered at smaller bandwidths than analog channels, thusallowing more digital channels to be transported without increasingbandwidth capacity of the transport system.

In embodiments, individual forward and/or return channels can beisolated using sub-band coding. By isolating individual channels, datarates and compression parameters can be customized and set on achannel-by-channel basis. Further, specific broadcast channels can bemixed with specific narrowcast channels, and the channels can betargeted at one or more designated nodes.

Methods, systems, and apparatuses are described herein that are operableto facilitate controlling and adapting forward and return information ona per channel basis. In embodiments, broadband compressed forward (e.g.,channels compressed downstream and received at a receiver) and remotePHY solutions (e.g., channels modulated at a receiver) can be combinedon a per channel basis. In embodiments, forward and return informationcompression parameters can be shaped at a sub-band level, thuspermitting needed transport capacity to be reduced. For example, theneeded capacity in digitized RF solutions can be reduced. Methods,systems, and apparatuses described herein are operable to facilitateintegration of broadband compressed forward and remote PHY solutionswhile supporting existing RF plant solutions.

In embodiments, lossless compression and de-compression techniques canbe used to deliver digitized broadcast and narrowcast (e.g., channelsdedicated for delivery of content to sub-groups) channels whileremaining within network and system capabilities. For example, ultrahigh speed analog-to-digital and digital-to-analog converters, alongwith Huffman compression and de-compression techniques can be used todeliver a digitized full-spectrum forward data path.

In embodiments, a CMTS output stage is an IFFT. Both the IFFT input andthe IFFT output includes the same information, but the information isrepresented in different domains (e.g., frequency/time domains).Therefore, in embodiments, a CMTS can provide the IFFT input data (e.g.,pre-IFFT data that remains in the frequency domain) to a digital forwardtransmitter, thus bypassing multiple network components (e.g., CMTSIFFT, digital-to-analog (DA) converter, RF amplifiers and combiners,analog-to-digital (AD) converter and statistical compression at thedigital forward transmitter, etc.). Separately transporting IFFT inputfrom the CMTS to a transmitter can reduce the amount of equipment andresources used at a headend and can reduce the net data rate on a fiberbecause only the real data is transmitted, thus making a greater amountof bandwidth available.

In embodiments, a narrowcast transmitter, using frequency sub-bandcoding, can output a plurality of narrowcast signals to a plurality ofsub-groups or nodes along a single optical link. The narrowcasttransmitter can output the plurality of narrowcast signals as multipleslices of spectrum, wherein each slice of spectrum is designated for aparticular sub-group or node. The narrowcast transmitter can furtherinstruct each receiver or node as to which slice(s) of spectrum to useand at which frequency to output the associated narrowcast informationto its intended subscribers. Spectrum slices may be directed atindividual node ports, replicated at multiple node ports or may beturned off. Thus, a single transmitter can feed narrowcast informationto multiple nodes or receivers along a single optical link.

In embodiments, frequency analysis and transformation back to the timedomain of frequency analysis data can create discontinuities (e.g.,increased impulse noise) at the boundaries of generated time domainwaveforms based on sub-band coded information in the inverse transform.Therefore, a need exists for improving frequency analysis andback-transform techniques to limit discontinuities at such inversetransform boundaries. Methods, systems, and apparatuses described hereincan facilitate leveling of sub-bands in the frequency domain, therebyreducing equalizing efforts and increasing channel capacity by reducingwasted bandwidth. Using a modulated lapped transform (MLT), one or morechannels from a first input can be inserted into the spectrum of asecond input, and the channel insertion can be accomplished without asignificant amount of noise addition to the individual channel(s) andwithout impulse noise as would be created when using, for instance afast Fourier transform (FFT) algorithm.

FIG. 1 is a block diagram illustrating an example network environment100 operable to facilitate converting an analog broadcast signal into adigital broadcast signal and combining the digital broadcast signal witha digital narrowcast signal. In embodiments, a broadcast signal (e.g.,BC signal) and one or more narrowcast signals (e.g., NC signals 1-n) arereceived at a headend 105. The broadcast and narrowcast signals can bereceived at the headend 105 as radio frequency (RF) signals.

In embodiments, a broadcast digitizer 110 digitizes a received analogbroadcast signal and forwards the digitized broadcast signal to abroadcast digital transmitter 115. In embodiments, the analog broadcastsignal is derived from digital bit streams that are quadrature amplitudemodulation (QAM) encoded and modulated. Within the broadcast digitizer110, a bandpass filter can filter the analog broadcast signal to filterout signals outside a predetermined frequency, and the resulting signalcan be converted to a digital signal, for example, by an AD converter.The digital signal can be filtered further (e.g., through a bandpassfilter), downconverted to a baseband signal (e.g., through a digitalmixer), and low pass filtered to produce a digitized signal.

In embodiments, the broadcast digital transmitter 115 receives thedigitized broadcast signal and converts the digitized broadcast signalto a broadcast optically modulated signal. For example, the broadcastsignal can be modulated at a wavelength designated for broadcastsignals.

In embodiments, one or more narrowcast digitizers 120 a-n digitize theanalog narrowcast signals and pass the digitized narrowcast signals ontocorresponding narrowcast digital transmitter(s) 125 a-n. In embodiments,the analog narrowcast signals are derived from digital bit streams thatare QAM encoded and modulated. Within each narrowcast digitizer 120 a-n,a bandpass filter can filter the analog narrowcast signal(s) to filterout signals outside a predetermined frequency range, and the resultingsignal can be converted to a digital signal (e.g., through an ADconverter). The digital signal can be filtered further (e.g., by abandpass filter), downconverted to a baseband signal (e.g., by a digitalmixer), and low pass filtered to produce a digitized narrowcast signal.

In embodiments, the digitized broadcast signal can have a frequency thatis within a frequency band at the bottom of the forward RF spectrum. Forexample, for a 54 MHz-1002 MHz forward RF spectrum, the bottom range(e.g., 54-522 MHz) can be reserved for digitized broadcast signals andthe upper range (e.g., 522-1002 MHz) can be reserved for digitizednarrowcast signals. This disclosure is not limited to any particulardigitizer, and any existing or future developed digitizer is intended tobe included within the scope of this disclosure.

In embodiments, the one or more narrowcast digital transmitters 125 a-nreceive the one or more digitized narrowcast signals and convert thedigitized narrowcast signals to narrowcast optically modulated signals.For example, each of the one or more narrowcast signals can be modulatedat various wavelengths, each narrowcast signal being associated with aspecific wavelength.

In embodiments, an optical multiplexer 130 combines (e.g., via densewavelength division multiplexing) the broadcast optically modulateddigital signal and the one or more narrowcast optically modulateddigital signals produced by the broadcast digital transmitter 115 andnarrowcast digital transmitters 125 a-n, respectively, to produce amulti-wavelength optically modulated signal. In embodiments, themulti-wavelength optically modulated signal is output to a downstreamvirtual hub 135 along an optical fiber.

In embodiments, the broadcast and narrowcast signals can be sub-bandfiltered using transform based filtering (e.g., MLT), compressed using alossless or lossy compression technique, and packed into a serialbit-stream sent to a receiver.

In embodiments, the multi-wavelength optically modulated signal can bereceived at a virtual hub 135. At the virtual hub 135, themulti-wavelength optically modulated signal can be demultiplexed by anoptical demultiplexer 140. Demultiplexing of the multi-wavelengthoptically modulated signal can result in the isolation of the broadcastsignal and the one or more narrowcast signals, and each of the one ormore narrowcast signals can be output to a targeted node (e.g., node 150a-n that the narrowcast signal is to be delivered to). In embodiments,the broadcast signal and a narrowcast signal can be multiplexed andoutput to a designated node 150 a-n. For example, the demultiplexer 140can isolate the broadcast wavelength and one or more sub-groups of oneor more narrowcast wavelengths. The broadcast wavelength can then besplit and combined with each of the one or more sub-groups of narrowcastwavelengths, and the combined wavelength can be forwarded onto adesignated node (e.g., nodes 150 a-n).

In embodiments, the demultiplexed broadcast signal can be output to abroadcast splitter 145, and the broadcast splitter can output thebroadcast signal to each of one or more nodes 150 a-n. Each of thedemultiplexed narrowcast signals can be isolated and can be output to adesignated node 150 a-n. In embodiments, each node 150 a-n can convertreceived broadcast and/or narrowcast optically modulated signals toelectrical signals. For example, nodes 150 a-n can decode the receivedsignals and recreate the original broadcast and narrowcast signals(e.g., the electrical broadcast and narrowcast signals as they werereceived at the headend 105). The nodes 150 a-n can then transmit theelectrical broadcast and/or narrowcast signals to a designated servicegroup or subscriber. In embodiments, the signal received at the node cancomprise multiple narrowcast signals and a broadcast signal, and thenode can demultiplex the received signal and output each narrowcastsignal, separate from the broadcast signal or combined with thebroadcast signal, to a designated receiver.

FIG. 2 is a flowchart illustrating an example process 200 operable tofacilitate converting an analog broadcast signal into a digitalbroadcast signal and combining the digital broadcast signal with one ormore digital narrowcast signals. The process 200 can begin at 205 whenan analog broadcast signal and one or more analog narrowcast signals arereceived at a headend (e.g., headend 105 of FIG. 1). In embodiments,each of one or more narrowcast signals received at the headend istargeted at a designated downstream component (e.g., node, servicegroup, customer premise, etc.).

At 210, the analog broadband and analog narrowcast signals can bedigitized. The analog signals can be digitized, for example, by one ormore digitizers (e.g., broadcast digitizer 110 of FIG. 1 and narrowcastdigitizer(s) 120 a-n of FIG. 1 respectively). For example, the analogsignals can be converted to digital signals and can be digitallyfiltered. In embodiments, the received analog broadcast and narrowcastsignals are digitized and passed onto a corresponding digitaltransmitter (e.g., broadcast digital transmitter 115 of FIG. 1 ornarrowcast digital transmitter 125 a-n of FIG. 1). In embodiments, thedigital transmitter can optically modulate a received signal, and canoutput the received signal at a particular wavelength.

At 215, the digitized broadcast and digitized narrowcast signals can becombined. The digitized broadcast and digitized narrowcast signals canbe combined, for example, by a multiplexer (e.g., optical multiplexer130 of FIG. 1). In embodiments, the optical multiplexer 130 combines(e.g., via dense wavelength division multiplexing) the digitizedbroadcast signal and the one or more digitized narrowcast signalsproduced by the broadcast digital transmitter 115 and narrowcast digitaltransmitters 125 a-n, respectively, to produce a multi-wavelength RFoptically modulated signal.

At 220, the combined digitized broadcast and narrowcast signals (e.g.,the multi-wavelength RF optically modulated signal) can be output tocorresponding downstream components. In embodiments, the combineddigitized broadcast and narrowcast signals can be output along anoptical fiber to a virtual hub 135 of FIG. 1. At the virtual hub 135, ade-multiplexer 140 of FIG. 1 can de-multiplex the receivedmulti-wavelength RF optically modulated signal and isolate theassociated broadcast signal and individual narrowcast signals. Inembodiments, the isolated broadcast signal can pass through a broadcastsplitter 145 of FIG. 1 and can be output to one or more nodes 150 a-n.Isolated narrowcast signals can be output to designated nodes 150 a-n.

FIG. 3 is a block diagram illustrating an example network environment300 operable to facilitate transporting a plurality of narrowcasttransmissions using a single transmitter. In embodiments, a transmitter305 receives a plurality of narrowcast signals from an upstream networkcomponent or content sources. In embodiments, a plurality of narrowcastsignals can be combined at a transmitter and output to one or morereceivers 310 along a single optical link.

In embodiments, the transmitter 305 may include a plurality ofanalog-digital (AD) converters 315. Narrowcast signals can be receivedat the transmitter 305 as RF narrowcast signals and can be passedthrough the AD converters 315, thus generating a plurality of digitalnarrowcast signals.

Digital narrowcast signals can be passed to a field-programmable gatearray (FPGA) 320. In embodiments, using a sub-band coding method, eachof the received narrowcast signals can be associated with and spreadover a plurality of frequency sub-bands. For example, a narrowcastsignal can be segmented and each segment can be associated with afrequency sub-band. In embodiments, a frequency analysis (e.g., Fouriertransform, modulated lapped transform (MLT), etc.) is performed on eachof the received narrowcast signals, and the output of the frequencyanalysis can be represented in frequency sub-bands.

In embodiments, the FPGA 320 encodes sub-bands that contain information,such as a certain group or number of channels (e.g., QAM channels). Inembodiments, the FPGA 320 can compress sub-bands into frames, and canoutput the compressed sub-bands to one or more receivers 310 along anoptical link (e.g., a high-speed optical link). For example, the FPGA320 can encode the narrowcast signals along with information identifyingdesignated receivers and/or ports for each narrowcast signal, as well asinformation designating sub-band frequencies at which to output eachnarrowcast signal.

In embodiments, delivery information (e.g., identification of the one ormore receivers, nodes, or ports that are targeted by the compressedsub-bands, identification of specific sub-bands designated for specificreceivers and/or nodes, identification of the specific compressionapplied to the sub-bands, original and target frequencies, etc.) can beoutput along with the compressed sub-bands. For example, deliveryinformation may include information allowing a downstream FPGA toreconstruct the narrowcast signals and output the narrowcast signals atdesignated sub-bands. The encoded narrowcast signals and deliveryinformation can be passed through an electrical-optical (E/O) converter325 and output along an optical fiber.

In embodiments, a receiver 310 can receive the compressed sub-bandsalong the optical link, and can identify one or more specific sub-bandsthat are designated for the receiver 310 (e.g., the sub-bands thatinclude narrowcast information targeted at the receiver 310). A signalreceived along the optical link can be converted to an electrical signalat the receiver 310 by an optical-electrical (O/E) converter 330. AnFPGA 335 can isolate the identified sub-bands (e.g., the sub-bandsdesignated for the receiver) and can generate one or more narrowcastsignals, each of the narrowcast signals being designated for a specificnode. In embodiments, the FPGA 335 identifies specific, designatedsub-bands and associates narrowcast signals with specific, designatednodes, based upon delivery information received from the transmitter305.

In embodiments, the FPGA 335 can use delivery information received inthe signal to reconstruct individual narrowcast signals. Deliveryinformation can instruct the FPGA 335 to identify segments associatedwith an individual narrowcast signal, wherein the segments are deliveredto the FPGA 335 at one or more different sub-band frequencies. Based onthe delivery information, the FPGA 335 can identify one or more sub-bandfrequencies and reconstruct a narrowcast signal from the informationcarried by the sub-band frequencies.

In embodiments, the FPGA 335 at the receiver 310 can receive a broadcastsignal. The FPGA 335 can combine the broadcast signal with each of theplurality of narrowcast signals and can output the multiple signalcombinations to designated nodes. In embodiments, each narrowcast signaloutput from the FPGA 335 is passed through a digital-analog (DA)converter 340. The narrowcast signals can then be output to designatednodes as analog narrowcast signals. De-compression can be applied toselected sub-bands of a signal output from the FPGA 335 and an inversetransform can transform frequency domain sub-band information back intoone or more time domain waveforms that are to be output at one or moreports from a corresponding node.

In embodiments, the FPGA 335 at the receiver 310 can identify anarrowcast signal or sub-band that is designated for a different FPGA orreceiver (e.g., FPGA 335′). The FPGA 335 can isolate the narrowcastsignal or sub-band designated for the FPGA 335′ and can output thenarrowcast signal or sub-band to the FPGA 335′. The FPGA 335′ can thenoutput one or more narrowcast signals through a DA converter 340′ andonto a designated node. Thus, the transmitter 305 can deliver narrowcastsignals that are designated for various different nodes and/or variousdifferent receivers.

In embodiments, an optical splitter 345 can identify designatedreceivers associated with sub-bands within an optical signal based onthe wavelength at which the optical signal is transmitted. The opticalsplitter 345 can route information associated with the sub-bandstransmitted at that wavelength to the designated receiver. For example,the optical splitter 345 can output information to a corresponding O/Econverter (e.g., O/E 330 or O/E 330′) where the signal can be convertedfrom an optical to an electrical signal. Narrowcast signals can then begenerated at a corresponding FPGA (e.g., FPGA 335 or FPGA 335′), and thenarrowcast signals can be passed through a corresponding DA converter(e.g., DA converter 340 or DA converter 340′). In embodiments, abroadcast signal can be split and routed to a plurality of receiversand/or FPGAs.

FIG. 4 is a flowchart illustrating an example process 400 operable tofacilitate transporting a plurality of narrowcast transmissions using asingle transmitter. The process 400 can begin at 405 when a plurality ofnarrowcast signals is received at a transmitter (e.g., transmitter 305of FIG. 3). In embodiments, narrowcast signals can be received at thetransmitter 305 as RF narrowcast signals and can be passed through theAD converters 315 of FIG. 3, thus generating a plurality of digitalnarrowcast signals.

At 410, one or more frequency sub-bands can be associated with each ofthe received narrowcast signals. Frequency sub-bands can be generated,for example, by an FPGA 320 of FIG. 3. Using a sub-band coding method,each of the received narrowcast signals can be transformed into one ormore frequency sub-bands. In embodiments, a frequency analysis (e.g.,Fourier transform, modulated lapped transform (MLT), etc.) is performedon each of the received narrowcast signals, and the output of thefrequency analysis can be represented in frequency sub-bands.

At 415, the sub-bands can be output to one or more receivers. Inembodiments, the plurality of sub-bands can be combined at a transmitter(e.g., transmitter 305 of FIG. 3) and can be output to one or morereceivers (e.g., receiver 310 of FIG. 3) on a single optical link orwavelength. In embodiments, sub-bands are compressed and serialized intoframes, and are output to the one or more receivers 310 along an opticallink (e.g., a high-speed optical link). In embodiments, deliveryinformation (e.g., identification of the one or more receivers that aretargeted by the compressed sub-bands, identification of specificsub-bands designated for specific receivers, nodes and/or ports,identification of the specific compression applied to the sub-bands,original and target frequencies, etc.) can be output along with thecompressed sub-bands.

At 420, a receiver can identify sub-bands designated for the receiver.In embodiments, a receiver 310 of FIG. 3 can receive the compressedsub-bands along the optical link, and can identify one or more specificsub-bands that are designated for the receiver 310 (e.g., the sub-bandsthat include narrowcast information targeted at the receiver 310). AnFPGA 335 of FIG. 3 at the receiver 310 can isolate the identifiedsub-bands (e.g., the sub-bands designated for the receiver), decompressthe sub-band information, combine sub-band information into a frequencydomain representation of one or more narrowcast signals, and use aninverse transform to transform the sub-band information from thefrequency domain to the time domain (e.g., FFT, MLT) to generate one ormore narrowcast signals, each of the narrowcast signals being designatedfor a specific node or node port. For example, the FPGA 335 canreconstruct narrowcast signals by combining segments of the narrowcastsignals carried by one or more sub-bands. In embodiments, the FPGA 335identifies specific, designated sub-bands and associates narrowcastsignals with specific, designated nodes, based upon delivery informationreceived from the transmitter 305 of FIG. 3.

At 425, narrowcast information can be output to associated output ports.In embodiments, a receiver can isolate digital narrowcast signals, cantransform the digital signals into analog signals, and can output eachof the narrowcast signals to targeted nodes. For example, the digitalnarrowcast signals can be output to a targeted node through a DAconverter (e.g., DA converter 340 of FIG. 3). In embodiments, eachnarrowcast signal can be combined with a broadcast signal, and thecombined narrowcast signal and broadcast signal can be output to atargeted node. In embodiments, the FPGA 335 at the receiver 310 canidentify a narrowcast signal or sub-band that is designated for adifferent FPGA or receiver (e.g., FPGA 335′ of FIG. 3). The FPGA 335 canisolate the narrowcast signal or sub-band designated for the FPGA 335′and can output the narrowcast signal or sub-band to the FPGA 335′.

FIG. 5 is a block diagram illustrating an example network environment500 operable to facilitate the downstream transporting and processing ofIFFT input data. In embodiments, a CMTS output stage is an IFFT. Boththe IFFT input and the IFFT output includes the same information, butthe information is represented in different domains (e.g.,frequency/time domains). Therefore, in embodiments, a CMTS can providethe IFFT input data (e.g., pre-IFFT data that remains in the frequencydomain) to the digital forward transmitter, thus bypassing a CMTS IFFT,digital-analog (DA) converter, RF amplifiers and combiners, as well asAD converter and statistical compression at the digital forwardtransmitter. In embodiments, IFFT input data may include payload dataand forward error correction (FEC) data.

Separately transporting IFFT input from the CMTS to a transmitter canreduce the amount of equipment and resources used at a headend and canreduce the net data rate on a fiber because only the real data istransmitted, thus making a greater amount of bandwidth available.

In embodiments, a CMTS 505 can identify data that is to be convertedfrom the frequency domain to the time domain. The CMTS 505 can outputidentified IFFT input data (e.g., data designated for transformationfrom the frequency domain to the time domain) to a transmitter 510. Inembodiments, identified IFFT input data can be output to the transmitter510 as a digital stream, and can remain in the frequency domain.

In embodiments, an RF signal can be received by the transmitter 510. TheRF signal may include content and associated data that is received fromvarious upstream sources, and may be received as an analog signal. Inembodiments, the RF signal can be digitized (e.g., converted from ananalog signal to a digital signal) by passing the RF signal through anAD converter 515. In embodiments, the digitized signal can then besub-band filtered and compressed at a statistical compressor 520.

In embodiments, IFFT input data can be received by the transmitter 510at a combiner 525, thus bypassing the AD converter 515 and statisticalcompressor 520. In embodiments, the compressed, digitized signal can becombined with the IFFT input data at the combiner 525, and the resultingaggregate signal can be output to a node 530. For example, the signalcan be output on an optical fiber.

In embodiments, the aggregate signal can be received at the node 530 bya receiver 535. The receiver 535 can identify and separate the digitizedsignal and the IFFT input data from the aggregate signal. Inembodiments, the digitized signal can be decompressed, and when sub-bandcoding has been applied at the transmitter, an inverse transform can beapplied at a statistical decompressor 540. In embodiments, the IFFTinput data can be passed through an IFFT 545 where the IFFT input datacan be transformed to the time domain. The IFFT output (e.g., the IFFTinput data represented in the time domain) and decompressed digitizedsignal can be combined by a combiner 550 and the combined signal can beconverted from a digital signal to an analog signal by a DA converter555. In embodiments, the combined analog signal can then be outputdownstream to a designated subscriber group or customer premise.

FIG. 6 is a block diagram illustrating an example network environment600 operable to facilitate the downstream transporting and processing ofIFFT input data. In embodiments, a CMTS 505 can provide the IFFT inputdata (e.g., pre-IFFT data that remains in the frequency domain) to thenode 530, thus bypassing a CMTS IFFT, digital-analog (DA) converter, RFamplifiers and combiners, as well as AD conversion and statisticalcompression at the digital forward transmitter. In embodiments, the CMTS505 can identify data that is to be converted from the frequency domainto the time domain. The CMTS 505 can output identified IFFT input data(e.g., data designated for transformation from the frequency domain tothe time domain) to a node 530. In embodiments, identified IFFT inputdata can be output to the node 530 as a digital stream, and can remainin the frequency domain.

In embodiments, an RF signal can be received by the transmitter 510. TheRF signal may include content and associated data that is received fromvarious upstream sources, and may be received as an analog signal. Inembodiments, the RF signal can be digitized (e.g., converted from ananalog signal to a digital signal) by passing the RF signal through anAD converter 515. In embodiments, the digitized signal can then becompressed at a statistical compressor 520. The digitized signal can beoutput to the node 530 along an optical fiber.

In embodiments, the digitized signal and the IFFT input data can bereceived at the node 530 by a receiver 535. The receiver 535 can outputthe digitized signal to a statistical decompressor 540 and can outputthe IFFT input data to an IFFT filter 545. In embodiments, the digitizedsignal can be decompressed at the statistical decompressor 540. Inembodiments, the IFFT input data can be passed through the IFFT 545where the IFFT input data can be transformed to the time domain. TheIFFT output (e.g., the IFFT input data represented in the time domain)and decompressed digitized signal can be combined by a combiner 550 andthe combined signal can be converted from a digital signal to an analogsignal by a DA converter 555. In embodiments, the combined analog signalcan then be output downstream to a designated subscriber group orcustomer premise.

In embodiments, broadband compressed forward (e.g., channels compressedupstream and received at a receiver) and remote PHY solutions (e.g.,channels modulated at a receiver) can be combined on a per channelbasis. In embodiments, forward and return information compressionparameters can be shaped at a sub-band level, thus permitting the sizeof set-up windows to be reduced. By reducing the size of set-up windows,the headroom needed in digitized RF solutions can likewise be reduced.Methods, systems, and apparatuses described herein are operable tofacilitate integration of broadband compressed forward and remote PHYsolutions while supporting existing RF plant solutions.

In embodiments, sharp filters can be used to select single channelswithin an RF spectrum. For example, an RF signal can be received at thetransmitter 510 and can be digitized by the AD converter 515. Inembodiments, the digitized signal can be filtered and divided into anumber of individual sub-bands. For example, the digitized signal can befiltered and divided into sub-bands by an FPGA 320 of FIG. 3. Inembodiments, each sub-band can be controlled individually, therebyallowing single channels to be isolated (e.g., single DOCSIS3.0/3.1 QAMchannels, single AM-VSB channel, etc.). A low speed communicationchannel can be embedded in a data stream, wherein the communicationchannel provides a table including the destinations of individualsub-bands. In embodiments, multiple destinations can be associated witheach sub-band to facilitate broadcasting of the same information to anynode connected to the same optical fiber link.

In embodiments, digitized RF channels can be selected on a per-channelbasis, and the channels can be placed at arbitrary output channelfrequencies. For example, an FPGA 320 of FIG. 3 can select individualchannels and can output the channels at arbitrary outputs. The FPGA 320can thereby generate channel combinations in signals that are customizedfor individual receiving nodes and/or ports.

In embodiments, a sub-band filter can cover a full spectrum (e.g., 0-1.4GHz of RF spectrum), such that channels of any type (e.g., broadcast,narrowcast, etc.) can be selected and directed to target nodes. SelectedRF spectrum channels can be mixed with R-PHY channels. For example, RFchannels and R-PHY channels can be combined at an FPGA 320 of FIG. 3.

In embodiments, BCF methods can be embodied in a broadband compressedreturn (BCR) transmitter. A BCR transmitter can compand data on asub-band level, thereby providing a constant SNR in each sub-band over awide input range without effecting adjacent, weaker channels (orsub-bands). Therefore, using such a BCR transmitter, additional headroombit-capacity is not required for ingress immunity, whereas adjacentchannels do not suffer when ingress occurs at a channel. In embodiments,the low band (e.g., 5-15 MHz) does not need encoding with very high SNR,as they do not support high order modulation formats, and the companderfunction can be set aggressively in the low-band, thereby reducing therequired bit rate without any impact on the MER of other frequencybands.

In embodiments, a transmitter (e.g., transmitter 510) can establish aspecific data rate for each channel, the data rate being such that oneor more performance requirements can be supported by the specific datarate. The data rate can be established, for example, by an FPGA 320 ofFIG. 3. Individual BCF channels can be isolated using sub-band codingmethods, and BCF channels can be mixed with R-PHY channels. For example,where each channel is associated with one or more sub-bands, individualsub-bands associated with a channel can be identified and isolated suchthat individual channels can be manipulated. In embodiments, thecombined BCF channels and R-PHY channels can be output and targeted toany one of multiple nodes.

In embodiments, a transmitter (e.g., transmitter 510) can applycompression and data rate parameters to individual return channels.Compression and data rate parameters can be applied, for example, by anFPGA 320 of FIG. 3. In embodiments, sub-band coding methods can be usedto create an optimized return system by establishing compression anddata rate parameters that are optimized for each individual returnchannel.

FIG. 7 is a flowchart illustrating an example process 700 operable tofacilitate the downstream transporting and processing of IFFT inputdata. The process 700 can begin at 705 when IFFT input data isidentified at a headend. In embodiments, a CMTS 505 of FIG. 5 canidentify IFFT input data (e.g., data that is to be converted from thefrequency domain to the time domain).

At 710, the identified IFFT input data can be delivered to a designatednode. For example, the IFFT input data can be delivered to a node 530 ofFIG. 5 as a digital signal and remaining in the frequency domain. Inembodiments, the IFFT input data can be output from a CMTS 505 to atransmitter (e.g., transmitter 510 of FIG. 5), combined with digitizedcontent (e.g., content received as an RF signal at the transmitter anddigitized at the transmitter), and output from the transmitter to thedesignated node 530. In embodiments, the IFFT input data can be outputfrom the CMTS 505 to the designated node 530. For example, the IFFTinput data can be received by a receiver 535 at the node 530, and thereceiver 535 can receive other data from a transmitter 510.

At 715, an IFFT can be performed on the IFFT input data. An IFFT can beperformed on IFFT input data, for example, by an IFFT 545 of FIG. 5 at anode 530 of FIG. 5. In embodiments, IFFT input data can be separatedfrom a combined signal (e.g., a combined signal including IFFT inputdata and a digitized signal) at a receiver 535, and the IFFT input datacan be output to an IFFT 545. The IFFT 545 can transform the IFFT inputdata from the frequency domain to the time domain.

At 720, the IFFT output can be combined with other digitized content. Inembodiments, the IFFT output (e.g., the IFFT input data that has beentransformed to the time domain) can be combined with other digitizedcontent at a combiner 550 of FIG. 5. In embodiments, the combined IFFToutput and digitized content can be converted to an analog signal (e.g.,by DA converter 555 of FIG. 5) and the combination of the IFFT outputand digitized content can be converted to an analog signal. The IFFToutput and digitized content can be converted to an analog signal, forexample, by a DA converter 555 of FIG. 5, and the analog signal can beoutput to a designated downstream target.

FIG. 8 is a block diagram illustrating an example transmitter 800operable to facilitate sub-band coding, monitoring, and compression. Inembodiments, a transmitter 800 may include an AD converter 810, a MLT820, a sub-band monitoring module 830, a sub-band level manipulatingmodule 840, a compressor 850, and an output interface 860. Thetransmitter 800 can receive analog narrowcast signals, broadcastsignals, or both, and the analog signals can be converted to digitalsignals at the AD converter 810. In embodiments, where a transmitter isintegrated in a CMTS, a digitized waveform may be provided directly tothe MLT 820, without first being converted to an RF signal at the CMTSand re-digitized by the AD converter 810.

In embodiments, methods, systems, and apparatuses can facilitateleveling of sub-bands in the frequency domain, thereby reducingequalizing efforts and increasing channel capacity by reducing wastedbandwidth. Using an MLT, one or more channels from a first input can beinserted into the spectrum of a second input, and the channel insertioncan be accomplished without a significant amount of noise addition tothe individual channel(s).

In embodiments, the digital signal can be encoded using an MLT at theMLT 820. Signals can be filtered at the MLT 820. For example, eachfrequency domain MLT coefficient permits phase and amplitudemanipulation to create an arbitrary filter response. Thus pre-programmedfilter responses can be created and applied, and adaptive filters can becreated and applied through a software interface.

In embodiments, sub-band levels can be monitored and/or adjusted by thetransmitter 800. Sub-band levels can be monitored by the sub-bandmonitoring module 830. For example, the sub-band monitoring module 830can monitor amplitude and phase of received signals. The sub-band levelmanipulating module 830 can recognize when adjustments need to be madeto corresponding MLT coefficients based on the sub-band levels monitoredat the sub-band monitoring module 830. In embodiments, the sub-bandlevel manipulating module 840 can adjust MLT coefficients at the MLT 820based upon amplitude and phase levels monitored by the sub-bandmonitoring module 830.

In embodiments, the transmitter 800 can output sub-band levels (e.g., asmeasured by the sub-band monitoring module 830) to an upstream ordownstream device, such as a device or server used to monitor thetransmitter 800. For example, an MSO or user can monitor and adjust MLTcoefficients at the MLT 820 based on the information received from thetransmitter 800.

In embodiments, the transmitter 800 can use the MLT 820 to manipulateboth amplitude and phase on a fine frequency scale to tune out amplitudeand/or phase errors. In embodiments, MLT coefficients can be set at theMLT 820 based upon feedback received from an external network monitoringdevice or server. For example, MLT coefficients can be set based uponequalizer corrections reported by a network monitoring device or server.Information associated with signal levels as transmitted by a headendand/or received by modems can be gathered and used to level sub-bands atthe transmitter 800. In embodiments, MLT coefficients can be based upona preset correction value. For example, MLT coefficients can be presetto account for a certain percentage of amplitude and/or phase errorsthat accumulate through network components (e.g., an amplifier chain inthe field).

In embodiments, noise spikes at transform boundaries due to quantizingthe transformed data at the transmitter 800 are prevented by using atransform method with overlapping transforms such as the MLT instead ofusing transforms that are not overlapping such as an FFT. Withnon-overlapping transforms, discontinuities occur at boundaries ofwaveform sections recovered from inverse transforms. Suchdiscontinuities can be understood as jumps in signal level that areequivalent to impulse noise. Whereas FFT methods can provide a propersignal to noise ratio, the signal to noise ratio only provides that theaverage signal to noise is acceptable. Impulse noise occurs with anamplitude much greater than would be expected based on Gaussianstatistics and causes bit errors in signals that are represented by theoutput waveforms (e.g., QAM signals). Using the MLT transform, suchdiscontinuities do not occur and the MLT can facilitate sub-band codingand quantization of arbitrary RF signals in order to obtain anacceptable performance free of impulse noise. It should be understoodthat MLT operations can occur in transmitters (e.g., transmitter 305)and in receivers (e.g., receiver 310).

In embodiments, signals can be compressed at the compressor 850 andoutput to a receiving node (e.g., receiver 310 of FIG. 3) through theoutput interface 860. Transporting digitized broadcast and narrowcastsignals may be limited by various network resources. For example,optical fiber links have a maximum payload capacity. A/D and D/Aconverters (e.g., AD converter 515, DA converter 555) have certainsample sizes and sample rates for accurately and efficiently convertinga signal. Therefore, a need exists for improved methods, systems, andapparatuses for transporting digitized broadcast and narrowcast signalsalong an optical fiber while providing A/D and D/A converters with asufficient sample size and sample rate.

In embodiments, compression techniques can be used to facilitate thereduction of required payload capacity associated with a digitizedfull-spectrum forward path. A digitized signal can be compressed using alossless compression technique (e.g., Huffman coding). Such techniquescan preserve end-to-end signal integrity, as indicated by performancemeasures (e.g., carrier-to-noise ratio (CNR), signal-to-noise ratio(SNR), noise-power-ratio (NPR), etc.). At a receiving node (e.g.,receiver 310 of FIG. 3), a corresponding de-compression technique (e.g.,Huffman decoding) can be used to reconstruct the original signalspectrum using an ultra-high speed D/A converter.

In embodiments, one or more compression techniques can be used tocompress a digitized forward signal to a size that is appropriate for acorresponding optical fiber. For example, a high-speed AD converter canbe used to convert a forward electrical data stream to a digital signal,the digital signal can be compressed using Huffman coding techniques,and the compressed digital signal can be output along an optical fiberto a receiving node. In embodiments, a compressed digital forward signalcan be de-compressed at a receiving node using Huffman de-compression,and the de-compressed digital signal can be converted to an analogsignal using a high-speed DA converter.

In embodiments, Huffman compression of a digital signal can use thestatistical distribution of the digital signal values to reduce thenumber of bits transmitted along an optical link. A “code-book” can becreated for the digital signal, wherein a one-to-one mapping existsbetween all possible signal values and a set of code-words that can betransmitted in place of each sample value. The code-words can bevariable in length, and the most probable signal values can be assignedto the shortest code words, while the least probable signal values canbe assigned to the longest code words. In embodiments, for a signal witha distribution of sample values that are Gaussian, for example, asignificant reduction in bit rate can be achieved using Huffmancompression.

In embodiments, Huffman compression of a digital signal generates a setof codes that does not contain pre-fixes, thus shorter code-words cannotbe construed as a prefix, or beginning, of a longer code-word. Using aset of codes without pre-fixes can allow for a simpler decodingalgorithm to be used at the receiving node.

In embodiments, the upper bits of each data sample can be compressed,and the lower bits of each sample can be transmitted uncompressed.Compression of the upper bits of each sample can result in moreefficient bit reduction, while transmitting the lower bits of eachsample without compressing the lower bits can allow for simpler and moreefficient decompression at a receiving node. For example, a smallercode-book can be used if the lower bits of each sample are leftuncompressed.

FIG. 9 is a flowchart illustrating an example process 900 operable tofacilitate transporting compressed digital forward signals along one ormore optical links. The process 900 can begin at 905 when one or morereceived electrical forward data streams are digitized. In embodiments,the electrical forward data streams are digitized by an AD converter(e.g., AD converter 515 of FIG. 5) at a transmitter (e.g., transmitter510 of FIG. 5). For example, the AD converter 515 of FIG. 5 can be anultra-high-speed AD converter.

At 910, the digital signal can be compressed and output to a receivingnode. In embodiments, the digital signal that is output from the ADconverter 515 can be compressed at the statistical compressor 520 ofFIG. 5. For example, the digital signal can be compressed using alossless compression technique (e.g., Huffman coding). In embodiments,the statistical compressor 520 can be an FPGA. After the digital signalis compressed, the compressed signal can be output along an opticalfiber to a receiving node (e.g., node 530 of FIG. 5).

At 915, the compressed digital signal can be de-compressed at areceiving node (e.g., node 530 of FIG. 5). In embodiments, thecompressed digital signal can be de-compressed at the statisticalde-compressor 540 of FIG. 5. For example, the digital signal can bede-compressed using a de-compression technique corresponding with thecompressed signal (e.g., Huffman de-compression). In embodiments, thestatistical de-compressor 540 can be an FPGA.

At 920, the de-compressed digital signal can be converted to an analogsignal. The de-compressed digital signal can be converted to an analogsignal, for example, by the DA converter 555 of FIG. 5. In embodiments,after the de-compressed signal is converted to an analog signal, theanalog signal can be output to a downstream network component.

FIG. 10 is a block diagram of a hardware configuration 1000 operable tofacilitate the transport of broadband digital forward data. The hardwareconfiguration 1000 can include a processor 1010, a memory 1020, astorage device 1030, and an input/output device 1040. Each of thecomponents 1010, 1020, 1030, and 1040 can, for example, beinterconnected using a system bus 1050. The processor 1010 can becapable of processing instructions for execution within the hardwareconfiguration 1000. In one implementation, the processor 1010 can be asingle-threaded processor. In another implementation, the processor 1010can be a multi-threaded processor. The processor 1010 can be capable ofprocessing instructions stored in the memory 1020 or on the storagedevice 1030.

The memory 1020 can store information within the hardware configuration1000. In one implementation, the memory 1020 can be a computer-readablemedium. In one implementation, the memory 1020 can be a volatile memoryunit. In another implementation, the memory 1020 can be a non-volatilememory unit.

In some implementations, the storage device 1030 can be capable ofproviding mass storage for the hardware configuration 1000. In oneimplementation, the storage device 1030 can be a computer-readablemedium. In various different implementations, the storage device 1030can, for example, include a hard disk device, an optical disk device,flash memory or some other large capacity storage device. In otherimplementations, the storage device 1030 can be a device external to thehardware configuration 1000.

The input/output device 1040 provides input/output operations for thehardware configuration 1000. In embodiments, the input/output device1040 can include one or more of a network interface device (e.g., anEthernet card), a serial communication device (e.g., an RS-232 port),one or more universal serial bus (USB) interfaces (e.g., a USB 2.0port), one or more wireless interface devices (e.g., an 802.11 card),and/or one or more interfaces for providing video, data, and/or voiceservices to a client device and/or a customer premise equipment device.In embodiments, the input/output device 1040 can include driver devicesconfigured to send communications to, and receive communications fromone or more networks (e.g., local area network, wide area network,optical fiber network, hybrid-fiber coaxial network, etc.).

Those skilled in the art will appreciate that the invention improvesupon methods and systems for delivering content to subscribers. Atransmitter, using frequency sub-band coding, can output a plurality ofnarrowcast and/or broadcast signals to a plurality of sub-groups ornodes along a single optical link. The transmitter can output theplurality of signals as multiple slices of spectrum, wherein each sliceof spectrum is designated for a particular sub-group or node. Thetransmitter can further instruct each receiver or node as to which sliceof spectrum to use and at which frequency to output the associatedsignal information to its intended subscribers. Thus, a singletransmitter can feed narrowcast information to multiple nodes orreceivers along a single optical link. In embodiments, channels can bemonitored and manipulated on a channel-by-channel basis, and channelsdelivered using different network solutions can be combined.

The subject matter of this disclosure, and components thereof, can berealized by instructions that upon execution cause one or moreprocessing devices to carry out the processes and functions describedabove. Such instructions can, for example, comprise interpretedinstructions, such as script instructions, e.g., JavaScript orECMAScript instructions, or executable code, or other instructionsstored in a computer readable medium.

Implementations of the subject matter and the functional operationsdescribed in this specification can be provided in digital electroniccircuitry, or in computer software, firmware, or hardware, including thestructures disclosed in this specification and their structuralequivalents, or in combinations of one or more of them. Embodiments ofthe subject matter described in this specification can be implemented asone or more computer program products, i.e., one or more modules ofcomputer program instructions encoded on a tangible program carrier forexecution by, or to control the operation of, data processing apparatus.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, or declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, or other unitsuitable for use in a computing environment. A computer program does notnecessarily correspond to a file in a file system. A program can bestored in a portion of a file that holds other programs or data (e.g.,one or more scripts stored in a markup language document), in a singlefile dedicated to the program in question, or in multiple coordinatedfiles (e.g., files that store one or more modules, sub programs, orportions of code). A computer program can be deployed to be executed onone computer or on multiple computers that are located at one site ordistributed across multiple sites and interconnected by a communicationnetwork.

The processes and logic flows described in this specification areperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output thereby tying the process to a particular machine(e.g., a machine programmed to perform the processes described herein).The processes and logic flows can also be performed by, and apparatuscan also be implemented as, special purpose logic circuitry, e.g., anFPGA (field programmable gate array) or an ASIC (application specificintegrated circuit).

Computer readable media suitable for storing computer programinstructions and data include all forms of non-volatile memory, mediaand memory devices, including by way of example semiconductor memorydevices (e.g., EPROM, EEPROM, and flash memory devices); magnetic disks(e.g., internal hard disks or removable disks); magneto optical disks;and CD ROM and DVD ROM disks. The processor and the memory can besupplemented by, or incorporated in, special purpose logic circuitry.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinvention or of what may be claimed, but rather as descriptions offeatures that may be specific to particular embodiments of particularinventions. Certain features that are described in this specification inthe context of separate embodiments can also be implemented incombination in a single embodiment. Conversely, various features thatare described in the context of a single embodiment can also beimplemented in multiple embodiments separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the embodiments described above should not be understoodas requiring such separation in all embodiments, and it should beunderstood that the described program components and systems cangenerally be integrated together in a single software product orpackaged into multiple software products.

Particular embodiments of the subject matter described in thisspecification have been described. Other embodiments are within thescope of the following claims. For example, the actions recited in theclaims can be performed in a different order and still achieve desirableresults, unless expressly noted otherwise. As one example, the processesdepicted in the accompanying figures do not necessarily require theparticular order shown, or sequential order, to achieve desirableresults. In some implementations, multitasking and parallel processingmay be advantageous.

We claim:
 1. A method comprising: receiving one or more analog signalsat a transmitter; converting the one or more analog signals to digitalsignals; segmenting each of the digital signals into a plurality ofsegments, each segment being associated with at least one sub-bandfrequency, wherein each respective one digital signal is segmented andeach respective one segment is associated with at least one sub-bandfrequency by performing a frequency analysis on the respective onedigital signal, the frequency analysis being performed using a modulatedlapped transform, and wherein each respective one digital signalcomprises information associated with one or more narrowcast signals,each narrowcast signal being associated with one or more sub-bandfrequencies, and each respective one digital signal further comprisesdelivery information, the delivery information identifying one or morereceivers for which one or more of the narrowcast signals aredesignated; and outputting the digital signals to a downstream networkcomponent, wherein each respective one digital signal is output as aplurality of associated segments, and wherein each respective onesegment is output at an associated sub-band frequency.
 2. The method ofclaim 1, wherein the digital signals are output on an optical fiber at asingle wavelength.
 3. The method of claim 1, wherein deliveryinformation is output along with the digital signals, the deliveryinformation comprising information identifying specific sub-bandfrequencies associated with specific signal segments.
 4. The method ofclaim 1, wherein one or more modulated lapped transform coefficients areupdated based upon signal errors identified at the transmitter.
 5. Themethod of claim 1, wherein one or more modulated lapped transformcoefficients are pre-set based upon signal errors expected during thetransport of the analog signals to the transmitter.
 6. The method ofclaim 1, further comprising: wherein each sub-band frequency isassociated with a channel carried by a signal; determining compressionparameters associated with each channel; and compressing each signalaccording to the compression parameters associated with each channelcarried by the signal.
 7. The method of claim 6, wherein the one or moreanalog signals comprise return signals.
 8. A method comprising:generating one or more narrowcast signals designated for one or morereceivers, wherein each respective one of the one or more narrowcastsignals is generated by combining sub-band frequencies associated withthe respective narrowcast signal; receiving a digital signal at areceiver, wherein the digital signal comprises information associatedwith the one or more narrowcast signals, each narrowcast signal beingassociated with one or more sub-band frequencies, and the digital signalfurther comprises delivery information, the delivery informationidentifying one or more of the narrowcast signals that are designatedfor the receiver; isolating from the digital signal, segments of thedigital signal comprising information associated with one or morenarrowcast signals that are designated for the receiver; generating eachnarrowcast signal designated for the receiver by combining sub-bandfrequencies associated with each narrowcast signal; converting theisolated segments of the digital signal generated narrowcast signalsinto one or more analog signals; and outputting the one or more analogsignals to one or more designated output ports.
 9. The method of claim8, further comprising: receiving a broadcast signal at the receiver; andcombining the broadcast signal with one or more of the generatednarrowcast signals.
 10. The method of claim 8, further comprising:wherein each sub-band frequency is associated with a channel carried bya narrowcast signal; receiving a pre-transformed signal comprising oneor more channels, wherein each channel is targeted for one or moredesignated output ports; and combining one or more channels associatedwith the pre-transformed signal with the one or more generatednarrowcast signals having the same designated output port.
 11. Anapparatus comprising: an interface configured to be used to receive oneor more analog signals; an analog-to-digital converter configured toconvert the one or more analog signals to digital signals; a sub-bandmodule configured to: segment each of the digital signals into aplurality of segments, each segment being associated with at least onesub-band frequency, wherein each respective one digital signal issegmented and each respective one segment is associated with at leastone sub-band frequency by performing a frequency analysis on therespective one digital signal, the frequency analysis being performedusing a modulated lapped transform, and wherein each respective onedigital signal comprises information associated with one or morenarrowcast signals, each narrowcast signal being associated with one ormore sub-band frequencies, and each respective one digital signalfurther comprises delivery information, the delivery informationidentifying one or more receivers for which one or more of thenarrowcast signals are designated; and an output interface configured tobe used to output the digital signals to a downstream network component,wherein each respective one digital signal is output as a plurality ofassociated segments, and wherein each respective one segment is outputat an associated sub-band frequency.
 12. The apparatus of claim 11,wherein each sub-band frequency is associated with a channel carried bya signal, the apparatus of claim 11 further comprising a compressionmodule configured to: determine compression parameters associated witheach channel; and compress each signal according to the compressionparameters associated with each channel carried by the signal.
 13. Oneor more non-transitory computer readable media having instructionsoperable to cause one or more processors to perform the operationscomprising: receiving one or more analog signals at a transmitter;converting the one or more analog signals to digital signals; segmentingeach of the digital signals into a plurality of segments, each segmentbeing associated with at least one sub-band frequency, wherein eachrespective one digital signal is segmented and each respective onesegment is associated with at least one sub-band frequency by performinga frequency analysis on the respective one digital signal, the frequencyanalysis being performed using a modulated lapped transform, and whereineach respective one digital signal comprises information associated withone or more narrowcast signals, each narrowcast signal being associatedwith one or more sub-band frequencies, and each respective one digitalsignal further comprises delivery information, the delivery informationidentifying one or more receivers for which one or more of thenarrowcast signals are designated; and outputting the digital signals toa downstream network component, wherein each respective one digitalsignal is output as a plurality of associated segments, and wherein eachrespective one segment is output at an associated sub-band frequency.14. The one or more non-transitory computer-readable media of claim 13,wherein one or more modulated lapped transform coefficients are updatedbased upon signal errors identified at the transmitter.
 15. The one ormore non-transitory computer-readable media of claim 13, wherein one ormore modulated lapped transform coefficients are pre-set based uponsignal errors expected during the transport of the analog signals to thetransmitter.
 16. The one or more non-transitory computer-readable mediaof claim 13, wherein the instructions are further operable to cause oneor more processors to perform the operations comprising: wherein eachsub-band frequency is associated with a channel carried by a signal;determining compression parameters associated with each channel; andcompressing each signal according to the compression parametersassociated with each channel carried by the signal.